Telephone-exchange system.



M. S. GONNER.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FIT-ED JULY 13, 1905.

Patented Oct. 20, 1908 3 SHEETS-SHEET 1.

I InvE'n r. MEL-FEE 5- Enrqggq $95M HIE met.

M. S. GONNER.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED JULY 13,1905.

Patented Oct. 20,1908.

8 SHEEN-SHEET 3. v

UNITED sTAtrEs PATENT OFFICE MERRITT, sf (BONNER, or noonnsrnn, New YonKfAssIeNoR To STROMBERG-OARLSON TELE- PHONE-MANUFACTURING COMPANY, OF noonnsrna, NEW YORK, A CORPORATION OF NEW YORK;

' .Specification of Letters Batent.

, TELEPHONE-EXCHANGE sizs'rEM.

Patented Oct. 20, 1908.

Application filed m 1a, 1905. Serial No. 269,465.

' To aZZ whom it may concern: 7

citizen of the United States, residing at Rochester, in the county of Monroe and State of New York, have invented a certain new and useful Improvement in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to telephone exchange systems, and particularly to the central exchange apparatus and arrangement thereof for signahng art -line subscribers.

It is desirable in signa ing a called sub scriber on a party line that upon insertionof the calling plug and actuation of the select: ive apparatus that the proper sign'alingcurrent is automatically connected with the line and is maintained in connection until the subscriber answers, whereupon the current flow is automaticallydiscontinued and the selective apparatus at the central exchange restored to its normal condition.

The object of my invention is to provide improved apparatus and arrangement thereof and accessory parts for such a system of .signaling. The selective switch mechanism and automatic controlling mechanism'there for are com rised in a unitary structure orv key, which ey, together with the signaling apparatus and circuits, forms the subject of t of connection, arrangement and construe my mvention.

The key comprises a plurality of selective keys, each corresponding to a substation con nected with the party-line. A locking bar is provided for. the keys for holding them-in their depressed position, and a controlling electromagnet serves to actuate the bar to lock the buttons'of the ke s in a depressed position. Each selective ey is" connected with asource of selective current, the signal receiving apparatus at av substation being adapted to respond to the current from only.

one of the sources. Upon-insertion of the calling plug into the jack of the called-line and upon depression of the proper selective button, a circuit will be closed through the controlling ma netu on engagement of contacts controlle by tlE ergijzation of this;controllingpiagnet causes, actuation of a ringing key to.connect the e depressed key. En-

calling plug with the ringing sources and also the controlling magnet, whereupon the ca 1- the depressed button. Signaling current Be it known that I, MERRITT' S. CoNNEn,

will then flow from the corresponding source through the ringing key contacts an (1 through the plug into the line to actuate the signal receivmg apparatus at the desired substation. The circuit through which this ringing cur- "rent flows includes the winding of a relay ver great on account of the high resistance bel s at the substation and a condenser in series therewith, and the relay is not sufliciently energized to influence the contacts controlled thereby, and the controllingmagnet will, therefor'e, remain energized to maintain connection of the signaling source with the line. When the subscriber, however, answers by removing'his receiver from the hook, he greatly reduces the resistance through the substation, and enough current will'now'fiow through the signaling circuit to energize the relay to actuate the contacts controlled thereby to open the circuit throu h ing' plug is disconnected from the signaling source and the locking bar released to allow return of the depressed button to its normal position with a consequent ru ture of the ringin circuit.

gether in the ordinary manner.

'My invention also includes other features tion, which will best appear withreferenee to ;the accompanying drawings,in which Figure 1 is adiagrammatic view showing a telep one exchange system in which my im-. proved apparatus is incorporated. Fig. 2 shows a modified arrangement.

underside of the top plate by the screws 5-5 as shown. These side bars or plates 3 and 4. 105

are bent atright angles to the sup orting bar 2 and form end we ls for the insu 'ating supporting base 6 in which are mounted the various springs of the switching mechanisms, a

causes actuation of the locking bar, to lock 1 plate? being secured to the insulating basefi 110 The called su scriber and 35 .the ca ling subscriber may 'now converse to- Fig. 3 is a plan view of the key structure employed.

-' 1414 which enga over the springs to hold them securely in position therein. The top plate has a series of openings 88 through w ich extend the stems 9' of the actuating buttons 10. Below the supof the locking bar has the larger opening 16 and the slot '17 therethrough, the edges 18 engaging in the slots 19 cut at the top of the end plate 3, and the locking bar is thus slidable within these slots.- The stem of each button is provided with an annular V-shaped cam or'rim 20, and below said cam or rim is the actuating button 21 of insulating .material for engaging the actuating springs 22 and 23. The rod or stem 24 extends mal downwardly from the actuating button and engages in the mounting base 6, a compres= sion spring -25 encircling this stem between the base 6- and the actuating button and tending to hold the button in its upper norosition. The diameter of the openings 12 t oug'h the lock plate is equal to the diameter at the edge of the V-shaped cams,

and when an opening'12 is directly below the cam of the correspondinglbutton and the but ton is depressed, there-will beno actuation of the locking bar. If an opening 12 is at either side jof the cam, actuation of the button will cause lateral movement of the locking bar. If a button is depressed to carry the cani'thereon below the edges of the corresponding opening in the lockin bar and the vented from being .raisedby its'restoring spring. It will be seen, however, that if another button be depressed the locking bar must necessarily be moved to allow passage i of the cam ofthe other button through corresponding .openin in the locking bar, and this, of course, wil move the lockin bar laterally, whereupon the firstbutton wi be 'released, the openin 12corresponding'to the first buttonhavin een moved'upon actuation of'the seconc button to allow assage therethrough of the cam of the first utton.

To cause lateral motion of the lockingbar to lock a depressed button, employ electro- --magnetic mechanism consisting of theelectromagnetframe. or yoke 26 secured tothe end late 3, the lower leg thereof being pro'-'.

vide with the pivot slot 27 in which pivots the V-Shapedend 28 of the electromagnet core 29 said core when brou ht into engagement with the upper leg or po e 30 of the elec-' tromagnet frame serving tocomplete the magnetic circuit. Surrounding the core is described when referring to Fig. 1.

ing bar is then moved latera ly and held, the depressed button will be locked and preto Fig. 1. 'The contacts or s I cam late passing through the-.'-.

the energizing winding 31 Whose leads 32are suitably connected in circuit, which will be The bridge piece 83 at the left hand end of the locking bar is normally disposed in the path.

of the upper end of the core, and upon ener:

will beattracted toward the pole 30 and the gization of the electromagnet this core end;

locking bar will be moved toward the right to lock any button whichinayliave been'depressed. Upon denergization of the electromagnet, the restoring spring of the deressed button will be sufficient to move the ocki-ng bar to its normal position as the button is moved upwardly and-the V-sha ed cam engages the edge. of the correspon ing opening 12 in thelock bar. The'screw 34,

passing loosely through the lower pole 26 and i into the core end, serves to maintain the core within the pivot slot, and to prevent lateral swing of the core the wings35-35 are provided, whi'ch'rest against the sides of the u per pole 30. This electromagnetialso rectly controls the ringing switching mechanism 36, whose actuating springs 37 and 38 connected with the end ofthe electromagnet through the insulating stud 38" are adapted to engage'either with the normal contact springs 39 and 40 or with the alternate contact springs 41 and 42 upon energization of the electrom'agnet; Eac buttonis' also as sociated 'withswitching mechanism 43 consisting of the actuating springs 22 and 23 in engagement with the actuating button and adapted'to normally engage the inner springs 44 and 45, and when the button is depressed to engage the alternate contact springs'46 and 47. A set-of circuit closing springs 48 upon actuation of the alternate contact s ring 'and 49 is provided for each'twoof the selective keys, the contact 48 being actuated 47 of the left hand button of the set v t rough the insulating disk or washer 50, while the spring 49 is moved upon actuation of the altern ate contact spring 46 of the right hand button of'tlie set. Thus upon depres siorr of either button of a set either the contact 48 or 49'will be moved to cause engage;

ment of these contacts to blose',a circuit which: will be describedlater with reference associated with thethirdan fourth buttons are connected these bhttonsi' A listening key 51 the handle 52- and the cam plate 53-mounted on the pivot late/1, this t 55 in the ate and through-the slot 'ITin the lock- The lower end 56 of the cam plate rod 54 passing through the top,

top ing, ar.

upo actuation of either of v 2115 rings48 and 49 engages .he rdllei' 57 upon actuation of the listening'keytoremove the main actuating;

spring 58 of the listening ke switching mach: amsm, this lower part 56 aving a flat "por tion 59 which, after actuation of the listeningp the actuating spring exerts a pressure along a line extending through the centers of the roller and the listening key ivot, and the key after actuation will be 100 ed. Extendingfrom the side of the end 56 is a pin or post 60 adapted, after the key has been -moved a distance toward its sition, to strike the extension 61 from the locking bar, and, therefore, when the listening key is actuated, the locking bar will be .moved laterally toward'the right Thus aflistening-in p0 ter the listening key has been moved to the listening-in position, actuation of a selective button will move the locking'bar toward ,the left to causerestoration of the listening key on account'of the engagement of the exten-' sion 61 with the post 60.

By means of the spacing stud the actue ating springs 63 and 64v are caused to move with the main actuating spring 58. The main actuating spring is normally free from contact, but upon actuation, of the key engages the contact spring 65. The actuating spring 63 is normally free from contact, but ,upon actuation of the key engages the contact spring 66. I The actuating spring 64 normally engages the contact spring 66, and upon actuation of the key engages the alternate contact 67. The contact spring 68 normally. engagestliie-associated spring 69, but upon'actuati'on of the key, the spring 68 is carried out of engagement by means of the insulating connection 70 between the springv 68 and the main actuating spring.

"Having'thus' described the general construction and arrangement of the key mechanism parts, I shal't'refer toFig. 1 and de scribe a telephone exchange system in which a key of this kind is utilized in connection with. controllingcircuits and other 'ap aratus. v p Thave shown a party'line A and a single .subscribers line B extending from the central exchange C. The limbs a and b of line B terminate in the armat'ures72 and 71,

the armature? 1 being normally in engage-- ment with its contact 73 connected With the grounded positive side of the common batteryS, while the armature 72 normally errgages its contact 74 connected with the negative side of the battery S through-the winding 75 ofi the indicating-relay 76. In this drawin the subscriber on the line B has initiatec? selective. key,in correspondence with the request. of the calling subscriber 'forfconnection with the substation A -moval of the. receiver at the 'callin sub- "station a circuit is immediately close from a callv by removing his receiver from the 'hook,lwhereupon central, after Upon re-- known condition of operatic n.1,

the source S through the substation transanswering .plug in the jack, causes closure ,of two circuits; one a local circuit from the negative side of the battery through the supervisory relay winding-79, through the sleeve; strand 80, through the sleeve 81 of the answeri lug, throu 'h the test thimble b P c 1 82 and through the wim ng 77 of the cutoii" relay to ground and thence to the grounded positive side of the battery. The other circuit closed upon insertion of the plug extends from the negative side of the battery through the winding 79, sleeve strand 80, sleeve 81, sleeve spring 83, line limb a, through the substation apparatus, through the line limb 7), through the tip jack s ring 84, through the tip member 85 of the .p ug, through the tip strand 86 and through the supervisory re a .y winding 87 to the positive side of the battery. Uponclosure of the local circuit just traced, the indicating relay becomes energized'to attract its armature whereby both line limbs are dis connected from direct engagement with the battery, and the indicating relay 75 being disconnected from circuit the indicating lamp controlled thereby is extinguished. The supervisory relay may be of a compound structure and arrangement as described in my Patent No. 799,146, Sept. 12, 1905. The armature 88 corresponding to the winding 87 is connected through an insulating stud 89 with the actuating spring 90, said spring 90. tending to engage with the contact spring 92. sponding to the winding 79 is normally. held in mechanical engagement against the armature 88 by the spring 94. Normally the spring 94 holds the spring 90 out of engagement with'the contact spring92, but upon current flow through the winding 79 the armature 93 becomes attracted away from mechanical engagement with the armature 88 and the s ring 90 .then moves into e,n' gage-ment witli the sprin 92 to cause closure of the local circuit inclur ing the supervisory lamp 95, this circuit includin the con ductors 96 and 97 leading to tie positive and negative side of the battery respec The armature .93 corretively'. The circuit through the substation .telephonic apparatus, however, being closed,

the winding 87 is energized and 'consequently the armature 88 is. attracted to -move. the sprin 90 away from the spring 92, whereupon tie supervisory lam '95 becomes extinguished; this being t e well;

Upon being notified of the desired connection by illumination of the indicating lamp 78,ithe erator, after insertion of'the answering p ug in the j ack, actuates the listening-key '51 to. connect her receiver 98in a circuit *which' may be traced as follows: from thereceiver to the alternates ring 67 ,tothe actuating spring 64, to the ca ling tipstrand 99, to thecondenser 100, to the answering tip 'stra'nd 86, through the plug; springjac'k and substation telephonic a paratus back to the answering sleeve stran 80, toxthe con denser 101, through the calling sleeve strand 102, and'through the main actuating listening key spring 58-, through the alternate contact spring 65 and back to'the receiver. The condensers 100and 101 render the cord'cir: cuit discontinuous to direct currents, but continupus-to telephonic currents, this being for the well known purpose of'p'roviding independent supervision ,for the-answering and calling studs ofthe cord circuit. 1 After having ascertained from the calling subscriber I that the subscriber at substation A is dedescription more clear, the reference charac ,associated'with the line A wil sired, the operator inserts thecalli'ng plug 103 into the spring jack associated with the lineA'; Through a similar circuit as traced inv connection with the apparatus connected with the line B the cut off relay "associated with the line A is energized. (To render the tem applied to the cut off and indicating mechanism and the supervisor? mechanism,

be primed.) The second supervisory circuit controlled by the substation apparatus at the-substation to be called is open and-the relay winding 87 is not energized and consequently the springs 90' and92 associated with said winding are in contact to close the circuit through" the supervisory lamp 95'. The operator now presses the second'key of the selective mechanism as shown,'whereu onthe following local circuit is 'establis edz from the positive-side of the battery'S'through cone ductor 104, through the winding 31 of the control-ling magnet, through ther'condu ctor.

105,.through. the closed contacts 69 and 68, through the conductor 106, -contact 107, ar-

mature108, conductor 1 9, co ductor 110,"

through the'contacts '48 and 49 hichwill be closed, and through the: conductor 111 to thene ative side of'the battery. Thus the .contro ing magnet immediately upon d'e pression of a selective key becomes, ener-' gized and, as-before described,"the cause of this is to move the locking bar 11 to lock the depressed key and also to move the actuat ng springs of the ringing switching mechanism to their alternate position to connect the-calling plug with the signaling current mechanism. J 1 Q I have here shown four selective keys cor responding to four substations and'also four sources 112, 113,114 and 115, each of a difqu'ent actuation of t cones:

ferent kind of signaling current.- These sources shownas generators'may' serve to produce currents of different frequencies which will actuate the corresponding signal receiving apparatus at the substation 'inde: pendently of each other, or thesev sources may produce currents of different harmonic pro erties,'or other currents'may be gener" ate from these sources so'that the current from one source when sent into ,thegline will 'actuateonly the signal receiving apparatus of the corresponding substation. Associated-with one terminal ring 117 formed of two insulated segments 117- and 117 one of-saidsegmentsbeing connected with the ring 116, the ot'her. segment being connected with a third contact ring 118, thethird contact rings of the enerators bein fall connected with groundor positive si of the battery, and the other terminal of each generator is connected with the negative side of the battery,

which may be-done through a common re- ,sistance or impedance; 119. Uponenergiza- 'tion of the controlling magnet and the consev e ringing key, two cir-. cuits are alternately closed through the signal of each gen- I .erator is a contact ring 116- and a contact receiving ap aratus at the substation to be called depen ing upon which of the segments 117 01117 of the second rin 117 is connect ed with the collector brus 120. If this brush 120 is, connected with the segments 117 as shown, current willflow as follows:

.limb I), through the si nal bell 128 at 'theidesired substation A t rough the condenser 129, back through the line limb n), through the sleeve spring 83, throu h thesleeve 130 of the calling pl-11g, 'throug the conductor 131, through the contacting ringin key springs 38 and 42, through the con uctor 132, through engaging sprm s 23 and 450tthe first selective key, throng the conductor 133, :through'the engaging springs 23"and 47 ofjthe depressedselective key, and through the conductor 134 to the 'other'terminal of the generator 113. {If the segment 117 however, is in contact with the brush-120,

current willflow as follows: from the positive side of'the battery togrotind, thence to conductor 135, to "the contact ring 118 associated with the generator 113, to the segment 117 tothe rush 120, 'and'fr'omthence to the same circuit through the various switch springs and through the substation signal receivin apparatus back to "the con- (i from: thence through the im-'- ductor 134 an pedance 119 and through conductor 111 to the negative side of the battery. "This in-.

j ated. The currents from the -.from the generator 1 l3 bothpass through the terrupted' direct current is of such character as not to cause actuation of the signalbell' at 1 the called substation, which bell is res onsive only to the current emanating from t e gen-" erator 113 during the time that the segment 1 1 7 'is connected with the ringing circuit, and thus the signal bell is interru tedly actuattery and relay 124, but'as the signal bells and the condenser at the substation are designed to offer f alarge resistance, this-relay 124 will not be a energized, and consequently the armature 108 will remain in. engagement with the contact 107 to'maintain closure'ofthe local circuit through the controlling magnet winding 1 31; Upon receiving these signals, however, .the called subscriber answers and removes his receiver from the hook, thereby offering a com arativelydow resistance path between the ine limbs. and thus sufficiently reducing the resistancein the ringing circuit to allow energization of the relay 124 which thereupon causes disengagement of thearmature '108 :from its contact 107 to open the local circuit through the controlling magnet, theresult being that the ringing key released to dis-' connect the calling-plug from the signaling apparatus and release of the locking bar to a ow. restoration of the second selective plugwhich was depressed.- To indicate tojthe operator the working condition of the ringing circuit and. also to assist in indicating when the called subscriber answers, a pilot relay 136 is included in each conductor 121, and

- the conductor 13'7 connectedwith each of the contacts 138 is connected with the negative j side. of the battery through the 'l39, b'h6'31'IIl&tll1GS 140 of the pilot relays pilot lamp beingconnected through-the common conpositive sideof t which remains illuminated scriber answers, I To assist in the..trans-- mission of the currents and in the control of, the relay 124 a condenser 142 may be bridged aboutzsaid'relay.

'duct0r141 -with'glround and thus with the tion, the corresponding pilot relay is energizedto close circuit throu h the pilot lamp It is sometimes'desirable for the operator tolisten-in.whileconversation is going on be- ""tween connected subscribers. .-Unless provision is made, however, actuation. of the listening key willopen thetip strand circuit uponfdisconnectionof thecontacts 64. and 66.

' To (prevent this. additional contact springs143 an" 144 are= provided for the su ervi'sory' relay mechanism, associated with t e calling .upon insertion of the callin spring jack, the Winding 79 wi lbe energized,

v and conductor 126 to the tip member "of the of the-listening. ke contacts.

e battery, and when the signaling current-flows to the called substauntil the jsubside'of the cord circuit, The spring connects with the switch spring 39. throughthe conductor145,and the spr1ng.143,connectswith the callingti strand of thecord circuit through the con uctor,-1 46.. Immediately asbefore described, and the armature 93 whlch has mechanical connectionwith thespring 143'through the stud 14 7 will be attracted/t0 engage the spring143with the contact. spring 144, and the tip" strand-circuit .is continuous through the. conductor 146, s ings 143 and 144, conductor 145', throug hsprings39 and 37 of the calling keyv plug inthe, I

calling plug, this circuit belngindependent This circuit just traced alsoena lesthe o erator to listen- 1n independently on the cal ing lugside as well each the'answering; lug si e.

. The local circuit inclu ing the winding of mallyclosed contacts 68 and 69 associated with the listening key. Should the operator listen-in while ringing. current is being ap& plied, theactuationof the listening key Wlll the controlling magnet also includes the noropen the contacts 68 and 69. and cause .de-

energization of. the controlling magnet which thereupon releases the locking bar to allow restoration of the depressed ringing key,

whereuponthe ringing circuit is interrupted.

To enable thegoperator to make a busy test, a test winding 148 is associated with the secondary wind' 1149 of the operators set,

one terminal of thlswinding being connected to -ground and thus with the positive-side of. the battery, while the other terminal is connected through conductor 1.50 with the actuating spring 63 of the listeningkey'. Upon actuation of the listening key the ti of the calling plu will be connected with t e positive. side 0 the battery through the condu'c tor 126, springs37 and 39, conductor-151,

listening key springs 66 and 63, conductor 150 and through the test Winding. 148 to ground and positive side of the battery]. vTo test, the operator touches one of t etest thimble's 152 with the .tip of the calling-plug. If the plug atfanother board'is inserted in the.

[corresponding multiple jack, shewill receive a click in the receiver. notifyin her-that the line is busy,the test circuit int at case being ble touched and through t e 'othertest think.

the

ductor 155. andthrough-tl1e Winding 7 9of the continued from thetest ti .to the test thinrbusy plug to the;

su ervi'sory relay mechanism to the negative side ofthe battery. If the busy plug is an answeringxplug the circuit 'will :be traced directly from the plug sleeve through the sleeve b conductor 80 ofthe busy cord circuit and from thence through the conductor 156 and through the "su 'ervisory winding 79 to :the negative side oi the battery. If the called there Will be no noise'or click in the operators receiver. 1

IrrFig. 2 I have shown asome'what simphfied arrangement of the selective key switch 15.ing mechanism and circuits." Each key is here provided with only the actuating springs 22 and 23 and the alternate springs 46 and 47 Upon depressionof the second-selective key the local circuit through the controlling elecwinding 31,- through conductor 105, through contacts 69 and 68 or the listening key, through conductor 106,through contact 107 through springs 23 and 47 of the second key and through conductor 1 1 1 to negative. battery, the electromagnet. causingja'ctu'ation ofthe locking'bar to lock the second key and to connect the ringing circuits With the calling plug at the ringing key 36. Signaling current from the generator 113 will alternately flow through the commutator ring 116 tothe '35 springs 46and 22 of. the second key, conductor 1'23, winding of the relay 124, through the springs41 and 37 of the ringing key, through the t p member of the plug, throu h signal receiving a paratus at the second su station,

40 back to we... sleeve member ofthe plug through conductor 131', springs 38, and 42of the ringing key. and conductor 132 back to.

the enerator, the signal receiving apparatus at t e substation being thus-actuated. j As flows during contact of the brush 120 Withv the segment 117 2 through the following-circuit: positive battery to ground, to the 118, segment-117 and from there through the same circuit as traced by the ringing circuit through the conductor Y132 and from there through the impedance Winding 119 back to negative battery, the purpose of this directv current flow "being, as before stated, for the purpose of providing current for'the relay '1241 to cause actuationthereof to open-the local circuit should the subscriber not hang his telephoneduring the time that the brush 120 is not connected with the generator. The arrangement ofall the other apparatus andthe circuits therefor remain asinFig. 1.

.I thus provide a very eflicient system and simple and compactapparatus} therefor,

- whereby to call a desired subscriber it is onlyline, however, is notjbusy, the test thirnbles thereof will not be charged and therefore.

tromagnet Will be as follows: from positive battery through conductor. 104,, through;

and armature'1-08, through conductor 109,.

segment 1.1.7, pilot relay 136, conductor 121',

closed. upon depression of said'selective key for causlng signaling current to-flow=from part ye substation.

in the system shown in Fig; 1, direct current 1 grounded conductor 135, through'the ring" necessary for the operator to insert the calling plug into the ack of thecalledline and to depress the selective key corresponding to the desired substation. The depressed key will be automatically "electroma netically locked to'maintain connection Wit the line of theproper source of ringing current'which flows intermittently through the signal jre- *ceiving apparatus at the selective substation until the called subscriber answers, Whereupon the central control of the electromagnetic locking mechanism is destroyed ,and the source of signaling current automatically dis connected from the line and without any as sistance or attention from the operator.

'As changes may readily be made in the ar% rangement and construction of the various :parts, I do not Wish to be limited'to the exact disclosure herein shown, but.

- Having described my invention, I desire to 85' secureby Letters Patent 1"."In 'a telephone exchange system, the

combination Witha telephone line extending from a central exchange to a plurality-"0t arty-line substations, a plurality of select We ringing keys at the central exchange, one corresponding to each substation, a controlling electromagnet"associated with said keys, a source of signaling current, means 1 adapted upon actuationof one of said select 'iv'e keys for closing a circuit through said" controlling elect rornagnet, mechanical means operated upon energization of said controlling ele'ctromagnet to lock said depressed key in its. actuatedposition, and a'second circuit said source into the line through signal receivin apparatus at the corresponding I 2. Ina tele hone exchan e system, the combination. 0 atelephone e extending from a central exchangejto' a pluralit" of party-line substations; a? plurality of [Se ectiveirnging keys at the central" exchange,

one corresponding to each substation, a controlling electromagnet associated with said keys, a source of signalingcurrent, means operated upon actuation of one of said selective keys for closing a circuit through said controlling electromagnet, means adapted .upon energization of said controlling electrotrolling electi'olnagnet associated with said keys, a source oi signaling current, means adapted upon actuation of one of said select 'ive' keys for closing a circuit through said controlling electromagnet, means adapted upon energization. of said controlling electromagnet for locking said depressed key in itsactuated position, a second circuit closedupon depression of said selective key for controlling as.

causing signaling current to flow from said source-into the line through signal IGOGHF ingap aratus at the corresponding partyline su station, adapted upon actuation of telephonic apparatus at the called substation to open the circuit through said controlling electromagnet whereby said actuated selective key 'is released'to cause 0 ening of the ringing circuit. 4. In a 'telep one exchange system, the combination with ar'telephone line extending from a central exchange to a plurality of party-line substations,,.a plurality of selective ringing keys at the central exchange, one corresponding to each substation, a controlling.. electromagnet associated with said keys, a source, of signaling current, means adapted u on actuation of one of said'select- -ive" evs or closing a circuit through said electror'nagnet, means adapted upon energization of said controlling electromagnet for locking said depressed key in its sitionga source of cuitmcluding said actuated position, a second circuit closed upon depression of said selective key for,

causing signaling current to flow'from said source into the line through signal receiving apparatus at the correspondingparty-line substation, and electromagnetic means controlled by the ringing circuit and adapted upon actuation of telephonic apparatus at the called substation'to open the circuit through the'controlling electromagnet iii-"hereby the-actuated selective key is released to circuit.

5., In a te ephone exchange system, the combination with a telephone line extending from a central exchange and connecting with aplurality of party-line substations, of a plu-v rality, of selective keys atthe central ex- -change,.one corresponding to each substatiou;

a controlling electromagnetassociated with said selective keys, a localcircuit including said controlling .electfroinagnet and, closed on ke s, means actuated upon current ly upon. actuation of 'one of said selective flow throng the said electroma net to cause the actuated'selective key to bis-locked in poringing current, and a' cirsource of signaling current closed. upon actuation of said selective key to send signaling current-into the line through and electromagnetic means pl'urality'of selective keys,

the signal receiving a paratus at the desired I substation, said signa ing circuit being con trolled by the circuit conditions at the called substation.

6. In a telephone exchange system, the

'a plurality of party-linesubstations, of a'plura ity of manually operated'selective signaling keys at the central exchange, one corresponding to each of the substations, a source of signaling current, a circuit closed to include.

said source and the signal receiving ap aratus at a substation upon actuation o the corresponding selective key, electromagnetic means controlled upon actuation of theselective key ,to lock said key in its actuated position whereby said source is maintained in connection with the signal receiving ap aratus, and means governed'bythe condition electromagnetic mechanism. to release the actuated'selective key. I

' 7. In a telephone-exchange system, the

combination with av telephone line extending from a with a central exchange and connecting lurality ofparty-line substations, ol'

'85 of the signaling circuit for controlling the' a plur'aity of manually operated selective signaling u corresponding to each of the substations, a source ofsignaling current, a circuit closed to include said source and the'signal receivin apparatus at a, substation upon actuation-o the corresponding selective key, electromag netic means controlled upon actuation of the selective key to lock said key in its actuated vs at the central exchange, one I position whereby said source is maintained in connection with thesign a] receiving appa ratus, and .electro magnet means governed by the condition of the signaling circuit for controlling the electromagnetic mechanism to release the actuated selective key.

8. In a. telephone exchange system, the combination with a telephone line leading from a central exchange-and connecting with a plurality of party-line.substations, of a one corresponding to each substation, a source of signaling cur- Y rent-at the exchange; actuation of one of said selective-kc s causing closure of a circuit throughsau source and connection thereof with the signal receiving apparatus at the corresponding substation',- electromagnetic inean's associated with said. keys, locking means controlled by the electromagnetic means, and-a local circuit including said electromagnetic means; actuation of the selective key causing closure of said local circuit and actuation of the lockin g'means for locking said key in its actuated position whereby said si naling circuit is maintained closed, said loca circuit being controlled by the condition of saidsignalin'g circuit.

9. In a telephone exchange system, the

combination with" a telephone, lineleading from a central exchange and connecting with a plurality of party-line substations, of a plurality of selective keys, one corresponding to each substation, a source of signaling current at the exchange, actuation of one. of said selective keys causing closure of a circuit through said source. and connection thereof .withthe signal receiving ap aratus at the corresponding substation, e ectromagnetic means associated :with said keys, locking closed, said local circuit being-controlled by the resistance condition of' thesignaling circuit. i r 10. In a telephone exchange system, the

combination with a telephone line leading from a central exchange and connecting with a lurality of party-line substations, of aplura ity of selective keys, one. corresponding to each substation, a source of signaling current at the-exchange, actuation of one of said selective keys causing closure of a circuitthrough said source and connection thereof. wlth the signal receivingap aratus at the corresponding substation, e ectromagnetic means associated with said keys, locking means controlled by the electromagneticv means, and a local circuit including said electromagnetic means, actuation of the selective key causing closure of 'said'local'circuit and actuation of thelocking means for locking said key inits actuated position whereby said signaling circuit, is maintained ClO SGCl SQJd local circuit being controlled by the substation apparatus.--

11'. In a telephone' exchange 'system, the combination with a telephone line leading from a central exchange and connecting with v a substation, of a key at the central exchange,

electromagnetic mechanism associated with said keyfa local'circuit closed through said electromagnetic mechanism u on actuation of said key, means whereby sai key is locked in its actuated position upon closure of said local circuit, a source of ringing current connected with signal receiving a paratus at the substation upon actuation'oi means governed by said-signaling circuit for controlling the local circuit through said electromagnetic mechanism. a I

12. In a telephone exchange system, the combination with a telephone line leading from a central exchange. and connecting with a substation, of a'key at the central exchange, electromagnetic mechanism associated with said key, a local circuit closed through said electromagnetic. mechanism u on actuation of-saidkey, means whereby sai keyis locked in its actuated position upon-- closureofsaid said key, and.

" local circuit, a source of ringing current con neoted with signal receiving a paratusat the substationupon actuation-o said kefi], and

electromagnetic means included in said sig'--.

naling circuit for controlling said local circuit.

through'the electromagnetic mechanism.

13:. In a telephone exchange system, the combination with a telephone lineextending from a central exchange and connecting with a substation, of switching mechanism at the central exchange, a source of signahng cur-- rent, actuation of said switching mechanism causing connection of said source with signal receiving. apparatus at-the substation, and

electromagnetic mechanism adapted upon actuation. of "said switching mechanism. to cause mechanical locking of the switching mechanism in its actuated position whereby said source is' maintained in connection with the substation, the circu'itthrou'gh said electromagnetic mechanism being controlled the electrical condition'of the signaling c rcuit.

14. In a telephone exchange system, the

combination with a telephone line extending from a central exchange to a substatiom t switching mechanism atlthe exchange associated with the line, a source of signaling currentadapted to send signaling current into- 1 the line and'through signal receivingf apparatus I at the substation upon actuation of said switching mechanism, a relay included in said circuit, a local circuit controlled by said relay, and electromagnetic mechanism included in said local circuit, and. adapted upon actuation of said switching mechanism to'lock said switchingmechanism in its a'c;

tuated positionwhereby said source is main tained in connectlon with the substation,

said signaling circuit upon closure thereof at. the substationthrough the signal .receiving-appar atus being of too high resistance. to allow actuation of said relay whereby said local circuit 1s unaffected, inclusion in circui-t of telephonic apparatus at the substation,

however, decreasing the" resistance of the signalingcircuit sufficiently toallow ener-" gization of said relay, whereby said local circuit is interrupted and said switching mech-.

anism released to. disconnect the source'fro'm I the substation.

15.111 a telephoneexc'ha'nge system, the combination with atelephone line extending from a' central exchange to a substation, of'

switching mechanism at the central exchange connected with the line, a source of signaling current at the central exchange connected with the line and with the substation-upon actuation of said switching mechanism, a relay in said signaling'circuit, alocal circuit controlled by saidrelay, and-electromagnetic mechanism in said local circuit adapted upon actuation of said switchingmechanism to lock said switching mechanism in- 'its' actuat'ed position tomamtain connection of said telephonic apparatusat the substation in re- 'throu' h the electromagnetic" mechanism "-where y said switchin mechanism is re leased and the source 05s I ;-connected from the substation.

cswitching mechanism at the central exchange adapted u on actuation to close two circuits,

through the line and to the substation, and

- switching mechanism at the central exchange cuit and adapted to cause said switching mechanism to be locked in its actuated posi- 5 condition of the signaling circuit when connected through the signal receivingap as'aid relay. and the local circuit controlled resistance COIldil'JOIIS sufiiciently to cause acof said electromagnetic mechanismi'olr looking the switching mechanism in its actuated upon changeof the resistance conditions at 'the substation upon actuation of substation sponsive to open the second. circuit whereby t source with thesubstation, the resistance rjatu's only at the substation being such t at thereby remain unaffected, the actuation of sponse'to the signal received changing the tuation of the relay to open the local circuit ignaling current is 16. In a telephone exchange system, the combination with a. telephone line extending from a central exchange to a substation, of

one of sai circuits includin electromagnetic mechanism, means adapte upon actuation position, a; source ofringing current in the other circuit for s'endingsignallng current electroma netic mechanism associated with the second circuit for controlling the continuity of the first circuit, said second circuit electromagnetic mechanism being responsive the substation to open said first circuit.

. 17. In a telephone exchange system, the combination with a. telephone line extending from acentral exchange to a substation, of-

connected Withthe line and adapted upon actuation to'close two circuits, a source of signaling current included in the firstv circuit tosend signaling'current'through the line to the substation'an'd primarily through the Signal receiving apparatusthereat, electromagn-etic" mechanism included in the second cir-' tion, and electromagnetic means in the first circuit controlling the continuity of the sec 1 0nd circuit, the electrical conditions of the signaling circuit when continued through the signal receivingapparatus' only at the sub y station being such that the electromagnetic means and the circuit controlled thereby remain unaffected, changes in'. the resistance at apparatus in response to the signals received by the signal receivmg apparatus causing sald electromagnetic meansto ecome re-' 7 e switchin mechanism is released to also dlsconnect t e signal 1 current source from circuit.

18. In a telephone 'exchange'systern, the

combinationwith. a telephone line extending from a central exchange to a substation, the

path at the substation normally extending i only ithroughsignal receiving apparatus, switching mechanism at the central'exchange connected with the line, a sourceof signalin current at the central exchange. adapted upon actuation of said switching mechanism to be connected'with the line to send'sig'nal ing' Ciiirrent through the signal receiving apparatus at the substation, electromagnetic mechanism at the central exchangefor'locking said switching mechanism'in its actuated position to m aintain'c onnection of said signaling source with the substation, and additional electromagnetic mechanism included 'in the signaling circuit andcontrolling the circuit for ener izing said electromagnetic mechanism, s'ai additional electromagnetic mechanism being normally irres onsive but adapted u on actuation of telep onic 'appa ratus at the substation to openfjthe circuit through the first electromagnetic mechanism, whereby said switching mechanism is released and the source of signaling circuit, disconnected from the substation.

19. In a telephone exchange system, the.

combination with a telephone line extending froma central exchange to a substation, of switching mejan's at the exchange connected with the line, a source of signaling current connected with the line upon actuation of said switching mechanism, the slgnalin circuitbeing normally continuous at the su station onlythroughthe signal receiving apparatus thereat, a relay included in the signaling circuit normally irres onsive to current flow I there'through, a loca circuit. controlled by said relay, electromagnetic mechanism controlled by said local circuit, means for causing said' electromagnetic mechanism-to lock said switching mechanism-in its actu ated position, whereby said source is maintained in connection with the substation, and means adapted upon actuation of other aparatus' at the substation for causing saidreay to become responsive and too'p en the receiving apparatus thereat, a relay included m the signaling circuit normally irresponslve to the current flow theretlirough, a local circuit primarily controlled by; said relay, an

electromagnet having a winding included in said local circuit and having-mechanical connection with said switching mechanism, said local circuit being secondarily controlled bfy lagg.

said switching mechanism'to close said circuit and to cause energization of said electromagnet to: cause sald swltching mechanlsm to be locked in its actuated position whereby said source is maintained in connection with the signal receiving apparatus at the substation, and means adapted upon actuation-of the telephonic-apparatus at the substationin response to actuations of the signal receiving apparatus for causing-said relay to-be'come responsive and to open said local circuit.

whereby said electromagnet becomes deenergized thereby to release the switching 'mechanism whereby said source is disconnected'from the substation. v

21. In a telephone exchange system, the

combination witha telephone line extending from a central exchan e to a substation, of a key at the central exc ange connected with the line, asource of signaling current adapted .fOIfiODIlQCtlOD with the line upon actuation of said key, a relay included in the signaling circuit, the signaling circuit being normally continuous at the substation through a high resistance. signal receiving circuit, whereby" said-relay is normally irresnonsive, an. electrocombination with a telephone line extending from a central exchange to a ive signaling magnet, alo'cal circuit inc uding the electro- Ina et windinggand primarily controlled by sa' relay, said ey havin secondary control over-'said'local circuit an adapted upon ac-- tuation' to close the local; circuit whereby saidlelectromagnet -becomes energized, and locking mechanism intervening between said electromagnet and said key whereby said key is locked in its actuated. osition when the: electromagnetjis energize said relay upon-v actuationj of the .lower resistance telephonic the connection of ringing current-with theline, a common electromagnetic means asso ciated with said selective keys and'with said main ringing key, a circuit closed through said electromagnetic means. upg'n actuation of onepof "said selective keys; whereby said 1 main ringing key is .actuated 'and the corresponding source of "signaling: current con-j nected with they line to influence the signal} receiving apparatus at". the corresponding substation, means operableupon actuation ;of said electromagnetic mechanism forlocking said key it's actuated position whereby sald source is mam'tamed m cbnnection with the line, and. additionalelectromagnetic.

release the key whereby the source of-si'gnah and adapted upon actuation of the telephonic a paratus at the called substation to open t e'energized' circuit ior saidflrst electro-' magnetic mechanism whereby said main ringin key and said actuatedsel ective key 'are're eased to open the signaling circuit.

23.' In a telep one exchange system, the

combination with a telephone line extending from a central'exchan e toa plurality of art 'line substations, o a plurality of select-' ive eye at the'central exchange, one correspending to each substation, a selective currentsource for each key, a main ringing key for determining the'conncction of signaling current with the line, an electromagnet, mechanism connecting said I elec'tromagnet with said mainringingkey and with the selective keys, a relay in. the main ringing cir-z cuit normallyirresponsive to current flowing through the sign'alreceivingapparatus only at the'substation, a local circuit partlycontrolled by said relay and including the winding of said electroma net, actuation of a selective key causing cosure of said local circuit, means operab eupon energization of the electromagnet for causing the mechanismcontrolled thereby to actuate the main ringing ke to connect the corresponding source with-t e line and to lock theselective key in its actuated position to maintain connection of the source with the line and means o'perable upon actuation. of the tele honic ap paratusatthe called substation for causing said relay to become responsive to open the local circuit whereby the electromagnefibe comes deen'erg'ize'd to allow the 'mainvrin ing key and the selective key. to'return to t eir normalfpositions thereby to disconnect the source from the line.

24,, I-n-a telephoneexchan e system, the combination with: a telephone ine extending fromaflcentral' exchange to a substation', 0f

. switching mechanism at the central exchange "connected with 'the line, a'source'ofsi aling current adapted for connection with t e line uponactuatlonof said switchin mechanism, means for causing the current ow from said source to be intermittent, the ringing circuit being normally continuous onl t oug h the signal receiving apparatus at t e substation, means for causing other current to' flow' through the signaling circuit when current from said source-is not flowing, 'thesignal receiving apparatus being responsive only to the "current from said source, a relay in the signaling circuit normally irresponsiv'e to the-currents flowing throughthe-signaling circuit, electromagnetic mechanism-as s'o'ciatedu'riththe switching mechanism and controlled by said relay, said; electromagneticmechanism being. connected in circuit upon actuation of-said switching mechanism, means actuated by said electromagnetic mechanism for-loek n the switching-mach;

means associated with the signaling circuit ,anisnrin its actuate -.position .to"'maintaih connection with the line of the signaling cirresponsive to 'only the phonic apparatus at the substation for causnected from the line.

* from a central exchange to a substation,

switching sources in the signaling circuit, the signal re- 1 1905.

cuit normally mechanism associated with said switching mechanism and controlled by said relay, actuation of the switching mechanism causing actuation of the electromagnetic mechanism to lock the 1 switching mechanism in its actuated; posil tion-whereby the signaling circuit is mainthe l tained in connect-ion with the line,-and means connection of the currents with the line, and 1 means adapted upon actuation of the teleing said relay to become responsive to efl'ect denergization of-the electromagnetic mechanism, whereby said switching mechanism is released and the signaling circuit discon 25. In a telephone exchange system, combination with a telephone line extending e at, the exchange .coni neeted with the line, a source of signaling current at the central exchange, a source of other current at the central exchange, actuation of the apparatus at the substation forcausing said relay to become res energization of the e l anism whereby said mechanism ectromagnetlc mech from the line.

1n Witness vWhere(' f, my-name this seventh switching mechanism causing I hereunto subscribe cult, means for alternately connecting said'l day of July A. D., ceivin'g apparatus at the substation bein current m sai MERBITI S. CONNER.

source ofsignaling current whereby said Witnesses: signal receivin apparatus-Will be intermit- E. A. HAWKINS, tently actuate a' relay in the signaling cirl W. W. KINSLEYQ adapted upon actuation of the telephonic onsive to cause deswitching mechanism s y released to disconnect the slgnaling current 

